National Construction Rentals employees Miguel Frias and Francisco Stephens, left, erect fencing in preparation for the upcoming Vibes Concert at Seaside Park along Broad Street in Bridgeport, Conn. on Thursday July 18, 2013. less

National Construction Rentals employees Miguel Frias and Francisco Stephens, left, erect fencing in preparation for the upcoming Vibes Concert at Seaside Park along Broad Street in Bridgeport, Conn. on Thursday ... more

Francisco Rosario of Bridgeport wipes his brow as he works in the extreme heat installing temporary fencing for The Gathering of the Vibes music festival at Seaside Park in Bridgeport, Conn. on Monday, July 15, 2013. less

Francisco Rosario of Bridgeport wipes his brow as he works in the extreme heat installing temporary fencing for The Gathering of the Vibes music festival at Seaside Park in Bridgeport, Conn. on Monday, July 15, ... more

Fans listen to moe. perform at Ives Concert Park in Danbury, Conn. on June 1, 2013. The concert was the first of the season at Ives Concert Park. Gov't Mule, a Southern rock jam band, will perform with Nicki Bluhm & the Gramblers on Sunday. less

Fans listen to moe. perform at Ives Concert Park in Danbury, Conn. on June 1, 2013. The concert was the first of the season at Ives Concert Park. Gov't Mule, a Southern rock jam band, will perform with Nicki ... more

When two men mingled with a crowd of bystanders and set off two bombs at the Boston Marathon, they killed three people, injured hundreds more and triggered a manhunt that shut down a large American city.

They also changed the way security is handled at high-capacity events.

But even at events with smaller-sized crowds, experts say, increasing security measures is now an inevitable part of the conversation. The Ives Concert Park in Danbury sees as many as 5,000 people at its summertime events.

As Bridgeport gears up for its annual Gathering of the Vibes concert this week, regular attendees of the Alive@Five concert series in Stamford have also seen stricter security checks at the outdoor concert space.

The concert series has had to relax some of its measures, as concertgoers have complained and attendance has plummeted.

For example, a requirement that all patrons between the ages of 21 and 25 sign a Consumer Protection Liquor Control Division Age Statement Form -- or a signed statement saying that they are indeed the age that is listed on their ID -- has been relaxed.

At the Ives center, he said, officials held off on changes other locations have instituted, like a ban on backpacks and other items. Instead, they've added stricter inspection protocols and security cameras to their 40-acre venue at Western Connecticut State University.

"We have a responsibility to protect as best as we can," he said.

Instead, the Ives staff works closely with state police, Western Connecticut State University police and Danbury police on security issues. Those meetings have led to changes in security protocols and the addition of new features, like a security camera system.

"I don't want to go into too much detail because I don't want these things to be tested," Greenberg said.

Inspections of people coming into the park have also been ramped up this year. "It was done (before the Boston event), but not as thoroughly," Greenberg said. "We're checking everything now."

Because planned security measures can only go so far, organizers of concerts and officials said they rely on patrons and volunteers to report anything suspicious they may see.

It's something many people are already doing after the tragic event in Boston and mass shootings, like the 2011 shooting in Tucson, Ariz., that ended with six dead and 19 injured, including U.S. Rep. Gabrielle Giffords and the 2012 shooting in an Aurora, Colo., movie theater.

Many Connecticut residents are also still reeling from the December massacre of 26 people, mostly children, at Sandy Hook Elementary School in Newtown. Nearly 12 years after 9/11, these types of terrorist acts and mass shootings are no longer uncommon.